1. Field of the invention
This invention relates to a newly isolated protein from cow's milk and the use of the protein or antibodies thereto for the control of milk secretion in lactating animals.
2. Description of the Prior Art
The rate of milk secretion by a lactating animal is regulated by the frequency of milk removal. In other words, there Is a mechanism which acts to match the animal's supply of milk to the demand of her offspring or of a farmer's milking regime. Part of this control is achieved by the release of galactopoietic hormones during suckling or milking. However, studies by workers at the Hannah Research Institute, Ayr, Scotland on lactating goats have shown that another factor is involved. This is an inhibitor which decreases milk secretion at a local level, i.e. at the individual gland of an udder.
It has already been shown that the inhibitor is present in a goat milk fraction containing whey proteins of molecular weight 10-30 KDa, this range of molecular weights being determined by the nominal sizes of filters used in ultrafiltration of the whey. The effect has been demonstrated both in vitro and in vivo. The in vitro technique, described by C. J. Wilde et al., Biochem. J. 242, 285-288 (1987), consists in culturing explanted pieces of rabbit mammary with and without the milk fraction and demonstrating the inhibition of lactose and casein synthesis. See also G. M. Stewart et al., J. Endocrinology 118, R1-R3 (1988). In the vivo technique, C. J. Wilde et al., Quarterly Journal of Experimental Physiology 73, 391-397 (1988), the milk fraction was injected into a single mammary gland of goats via the teat canal. A temporary dose-dependent reduction of milk yield, specific to that gland, was observed.
It has remained a problem to determine whether an inhibitor is present in cow's milk and, if so, to purify it sufficiently for identification, with a view to chemical or biological synthesis.